Overview

Overview

There are two major categories of skin cancer - malignant melanoma and non-melanoma skin cancer (NMSC). This site is primarily concerned with NMSC, for which Metvix® is an important treatment option.

Malignant Melanoma

Malignant melanoma is a neoplastic proliferation of melanocytes occurring predominantly in exposed skin, but may also arise in any mucosal surfaces containing the original melanin-producing cells that migrated from the developmental neural crest.

Malignant melanoma is less common than non-melanoma skin cancer (NMSC), but is the most serious skin cancer in terms of mortality. It has a high potential for widespread metastasis and recurrence, and as a result is responsible for 77% of all skin cancer deaths1. Following metastasis, cancer cells can be found in the lymph nodes and other organs - typically lungs, liver, bowel, brain and bone.

Unlike NMSC which predominantly occurs in Caucasians, malignant melanoma is seen among all racial and ethnic groups2. Nevertheless, the incidence in individuals with highly pigmented-skin is only 1 per 100,000, compared to more than 50 per 100,000 in Caucasians1.

Prevalence is also influenced by the interaction of ethnicity with local geography and climate:

  • In Australia and New Zealand the incidence of malignant melanoma has been calculated as 37.7 per 100,000 for males and 29.4 per 100,000 for females.
  • In the USA the incidence is 6.4 per 100,000 for males and 11.7 per 100,000 for females1.

The risk factors for malignant melanomas are:

  • Sun exposure
  • Artificial UV sources
  • Skin type - i.e. fair skin, red hair/freckling of the skin

For further information on malignant melanoma including its diagnosis and treatment click here (by clicking on this link you will be leaving this site - Galderma is not responsible for the content).


Non-Melanoma Skin Cancer (NMSC)

NMSC is the major focus of this section since many forms are treatable with Metvix®. It is also the most common category of skin cancer, accountable for approximately 75% of all skin cancers3.

The vast majority of NMSCs fall into two categories: basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Since Metvix® is indicated for treatment of BCC and not SCC,  the reader is referred here for further information on SCC and its treatment (by clicking on this link you will be leaving this site - Galderma is not responsible for the content).

A third type of NMSC exists, and is termed Bowen's disease, also known as 'SCC in situ'. It also is treatable with Metvix®.

Although pre-malignant and not classed as a NMSC, actinic keratosis (AK; also termed solar keratosis) lesions are also significant as they are disfiguring and occasionally progress to become SCCs (an estimated 0.025->10% of AKs develop SCC per year11). Invasive SCC can be life-threatening. While some AK lesions will regress spontaneously, most persist. The risk of transformation is proportional to the number of AK lesions present. They are extremely amenable to Metvix® treatment.

AKs have tended to be under-treated, and the increasing incidence of SCC is probably at least partly due to this.
 
NMSCs have a very favourable prognosis if treated early and metastasis is rare.  However when left untreated,  many lesions - BCCs for example - can cause extensive local damage to surrounding skin and underlying tissues.  Moreover, NMSCs impact quality of life because they are cosmetically disfiguring.

NMSCs generally have a high recurrence rate.  For patients with NMSC, there is a 36%-52% probability that a new skin cancer will develop within 5 years2.

NMSC Epidemiology and Incidence

NMSCs are extremely common conditions. It has been estimated that there are 2.75 million new cases of NMSC diagnosed yearly across the globe4. BCC is the most common form, comprising 75% of all NMSCs and is therefore the most common malignant disease throughout the world. SCC accounts for 20% of all NMSCs4.

  • 900,000 to 1.2 million new cases of NMSC are diagnosed yearly in the US6.
  • 1.8% of the total population in Australia was treated for an NMSC in 20029.


Risk factors for NMSC

Typical risk factors for developing NMSC are:

  • Exposure to excess sunlight or UV radiation:
    • Incidence of NMSC in Caucasians increases proportionally with proximity to the equator, with the incidence of SCC doubling for each 8-10 degree decline in latitude due to UV light exposure. UV dosage per unit time at the equator in the Pacific is very high, about 200% that of Europe or the northern US, and 30% higher than that of the southern US2.
  • Age:
    • Both BCC and SCC increase in incidence with age. BCC has approximately a 5 times higher incidence in individuals over 75 years old, compared to individuals between 50 and 55 years old, and for SCC this figure is 35 times higher5.
  • Fair complexion.
  • Skin containing ulcers, scars or burns.

More detailed  information on specific types of NMSC is provided below.

A Growing Problem

  • The incidence of NMSCs continues to increase due to:
    • Aging populations.
    • Lifestyle changes and travel - leading to increased sun exposure.

For example, in Australia, the incidences of SCC and BCC rose by 133% and 35%, respectively, between 1985 and 20027. In Caucasian populations in Europe, the United States, Canada, and Australia, the average increase in incidence of NMSC is 3-8% per year since 19642.

Public health awareness campaigns combined with early diagnosis and treatment are the keys to stemming these trends.

References